A method of video processing includes deriving, for a conversion between a chroma block of a video and a bitstream representation of the video, parameters of a cross-component linear model by using downsampled luma samples that are generated from N above neighboring lines of a collocated luma block of the chroma block using a downsampling filter, where N is a positive integer; and performing the conversion using a predicted chroma block generated using the cross-component linear model.
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2. The method of claim 1, wherein in response to the chroma block having a color format of 4:2:2, a second above neighbouring line of the collocated luma block is excluded from being used to derive the downsampled neighbouring top luma samples.
This invention relates to video encoding and decoding, specifically improving chroma block prediction by selectively excluding certain neighboring luma samples during downsampling. The problem addressed is inefficient chroma prediction in video compression, particularly when handling 4:2:2 color formats, where chroma samples are subsampled relative to luma samples. In such cases, using all neighboring luma samples for deriving downsampled chroma samples can introduce artifacts or reduce compression efficiency. The method involves processing a chroma block in a video frame, where the chroma block has a 4:2:2 color format. When deriving downsampled neighboring top luma samples for chroma prediction, the method excludes a second above neighboring line of the collocated luma block. The collocated luma block is the luma block that spatially corresponds to the chroma block. By excluding this second line, the method avoids using potentially irrelevant or redundant luma samples, improving prediction accuracy and compression efficiency. The exclusion is applied specifically to the 4:2:2 format, where chroma samples are horizontally subsampled, making the second above line less relevant for accurate chroma prediction. This selective exclusion helps maintain consistency in chroma prediction while reducing computational overhead. The method may be part of a broader video encoding or decoding process, where chroma blocks are predicted using neighboring luma samples to enhance compression performance.
3. The method of claim 1, wherein in response to the chroma block having a color format of 4:2:2, a same downsampling filter is used to derive the downsampled neighbouring top luma samples regardless of whether the chroma block is at the top coding tree unit boundary or not.
4. The method of claim 3, wherein in response to the chroma block being at the top coding tree unit boundary, the downsampled neighbouring top luma samples are derived based on the nearest above neighbouring line of the collocated luma block.
This invention relates to video encoding and decoding, specifically improving chroma block processing at coding tree unit (CTU) boundaries. The problem addressed is the challenge of accurately deriving downsampled neighboring luma samples for chroma blocks located at the top boundary of a CTU, where traditional methods may fail due to lack of available reference samples. The solution involves a method for deriving downsampled neighboring top luma samples when a chroma block is positioned at the top CTU boundary. In such cases, instead of relying on unavailable samples above the boundary, the method uses the nearest available line of luma samples from the collocated luma block within the same CTU. This ensures that the chroma block can still be processed correctly by leveraging intra-CTU luma samples, maintaining encoding efficiency and visual quality without requiring additional data from adjacent CTUs. The method is part of a broader approach to chroma block processing that includes filtering and downsampling neighboring luma samples to generate reference data for chroma prediction. By handling boundary conditions explicitly, this technique avoids artifacts and improves compression performance, particularly in scenarios where CTU boundaries intersect chroma blocks. The approach is compatible with existing video coding standards and can be implemented in both encoders and decoders.
7. The method of claim 6, wherein the same filter coefficients are [1 2 1].
8. The method of claim 1, wherein a first syntax element specifying a maximum block size used for a transform skip mode is conditionally included in the bitstream based on a value of a transform skip enabled flag included in a sequence parameter set in the bitstream.
9. The method of claim 1, wherein the conversion includes decoding the video from the bitstream.
10. The method of claim 1, wherein the conversion includes encoding the video into the bitstream.
A method for video processing involves converting video data into a compressed bitstream format. The conversion process includes encoding the video into the bitstream, which reduces the data size while preserving visual quality. This method addresses the challenge of efficiently transmitting or storing high-definition video content by leveraging compression techniques. The encoding step ensures compatibility with standard video streaming and storage protocols, enabling seamless playback across various devices. The method may also include preprocessing steps to optimize the video data before encoding, such as noise reduction or frame interpolation, to enhance compression efficiency. Additionally, the encoded bitstream may be further processed for error correction or encryption to ensure secure and reliable transmission. The overall approach aims to balance compression ratio, quality, and computational efficiency, making it suitable for real-time applications like video conferencing, streaming services, and broadcast systems. The method can be implemented in hardware, software, or a combination of both, depending on the specific use case and performance requirements.
12. The apparatus of claim 11, wherein in response to the chroma block having a color format of 4:2:2, a second above neighbouring line of the collocated luma block is excluded from being used to derive the downsampled neighbouring top luma samples.
13. The apparatus of claim 11, wherein in response to the chroma block having a color format of 4:2:2, a same downsampling filter is used to derive the downsampled neighbouring top luma samples regardless of whether the chroma block is at the top coding tree unit boundary or not.
14. The apparatus of claim 13, wherein in response to the chroma block being at the top coding tree unit boundary, the downsampled neighbouring top luma samples are derived based on the nearest above neighbouring line of the collocated luma block.
17. The apparatus of claim 16, wherein the same filter coefficients are [1 2 1].
A digital signal processing apparatus filters input signals using a finite impulse response (FIR) filter with a fixed set of filter coefficients. The apparatus includes an input interface to receive an input signal, a processing unit to apply the filter coefficients to the input signal, and an output interface to provide the filtered signal. The filter coefficients are specifically set to [1 2 1], which defines a symmetric three-tap FIR filter. This configuration emphasizes the center sample while attenuating higher-frequency components, effectively smoothing the signal. The apparatus may be used in applications requiring simple low-pass filtering, such as noise reduction or signal conditioning in audio, sensor data, or communication systems. The fixed coefficient structure ensures consistent filtering performance without requiring dynamic adjustments. The processing unit applies the coefficients to the input signal in a sequential manner, multiplying each sample by the corresponding coefficient and summing the results to produce the filtered output. The apparatus may operate in real-time or batch processing modes, depending on the application requirements. The fixed [1 2 1] coefficients provide a balance between computational efficiency and filtering effectiveness, making the apparatus suitable for resource-constrained environments.
20. The apparatus of claim 11, wherein a first syntax element specifying a maximum block size used for a transform skip mode is conditionally included in the bitstream based on a value of a transform skip enabled flag included in a sequence parameter set in the bitstream.
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April 29, 2022
November 8, 2022
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